A discussion of the number of degrees of freedom, and their dynamical
properties, in higher-derivative gravitational theories is presented. The
complete non-linear sigma model for these degrees of freedom is exhibited using
the method of auxiliary fields. As a by-product we present a consistent
non-linear coupling of a spin-2 tensor to gravitation. It is shown that
non-vanishing (Cμναβ​)2 terms arise in N=1, D=4
superstring Lagrangians due to one-loop radiative corrections with light field
internal lines.Comment: 8 pages, LaTeX2e and AMS-LaTeX 1.2, Talk presented at SUSY'95, Ecole
Polytechnique in Palaiseau, Palaiseau, France, May 15-19, 199